Core taker devices



United States Patent M 3,220,493 CORE TAKER DEVICES Harold J. Urbanosky, Houston, Tex., assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Dec. 17, 1963, Ser. No. 331,236 4 Claims. ((31. 1754) This invention relates to apparatus for obtaining solid samples of earth formations and, more particularly, pertains to a new and improved core-taking apparatus for obtaining a solid sample of earth formation material.

Generally, cores or samples of earth formation material are obtained by lowering a side wall sample taker assembly into the borehole to the level of the formation to be investigated. The sample taker assembly includes a gun body which receives a number of hollow coretaking bullets together with explosive means which are selectively operable so that the bullets may be impelled toward and into a formation, with the hollow interior of the bullets thereby receiving the formation material. Usually, the core bullet is secured to the gun body by one or more flexible retrieving connections so that a pull, as by raising the gun body, serves to withdraw the core bullet with a formation sample from the earth formations. Thus, a formation core sample can be retrieved to the surface of the earth for examination and testing.

However, many problems are presented by the variety of formations which are encountered in sampling operations. For example, the types of formations may be generally classified as (1) soft, (2) medium, (3) firm, (4) hard, and (5) extra hard. Thus, the problems may vary from the difficulty in getting the bullet into the extra hard formations without damage to the difficulty encountered in soft formations in the withdrawal of the core bullet from the formation. To obtain core samples from the various types of formations, different types of core bullets have been designed to meet the various conditions arising. Aside from the problem of retrieving the core bullets, it is, of course, necessary to obtain a core sample which is representative of the formation tested.

Particularly in the soft to firm formations, recovery of core bullets has been facilitated by providing the core bullet with a separable forward portion in the form of an annular cutting ring which generally has a slightly greater outer diameter than the core barrel. Thus, the ring forms an enlarged hole relative to the body of the bullet to alleviate sticking of the bullet body in the formation. When a pull is exerted on the body of the bullet, it should separate from the cutting ring thereby to leave the cutting ring in the formation. Various cutting ring attachments have heretofore been used such as the types disclosed in Patents No. 2,923,530, No. 3,101,797 or No. 3,072,202.

It has been found in many instances that the core bullet becomes so firmly embedded that in pulling on the bullet in the formations, the wire-retrieving connections are broken.

Accordingly, it is an object of the present invention to provide new and improved core-taking apparatus for minimizing the retrieval pull required on a core-taking bullet.

Another object of the present invention is to provide new and improved core-taking apparatus which is selfretracting from earth formations.

Still another object of the present invention is to provide new and improved core-taking apparatus which is independently self-retracting from earth formations.

In apparatus for obtaining a core sample, in accordance with the present invention, a gun body receives one or more core-sampling bullets which may be disposed lengthwise of the gun body. The bullet is adapted to be im- 3,220,493 Patented Nov. 30, 1965 pelled toward and into earth formations by explosive means and has a body member with a cutting ring member releasably received on its forward end. Means are provided to operate after the bullet has left a gun body and is in the earth formations to move the body member rearwardly relative to the ring member. Thus, the body member is retractable from earth formations relative to the ring member independent of the usual retrieving wire members.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view in partial cross-section of apparatus embodying the present invention for obtaining a core sample and illustrated in a well bore;

FIG. 2 is a view in cross-section of a bullet embodying the present invention;

FIG. 3 is a view in cross-section of a bullet embodying another form of the present invention.

In FIG. 1 of the drawings, there is shown a gun block or body 10 disposed in a borehole 11 opposite a format1on 12 of interest. Usually, borehole 11 contains a drilling mud 13.

Gun block 10 has a cylindrical bore 14 adjoining a bore 15 of smaller diameter, the bore 15 forming a powder chamber which terminates short of the rear surface 16 of the gunblock. Chamber 15 contains an appropriate and convenuonal explosive propellant 17 while bore 14 receives a generally cylindrical core-taking device or bullet assembly 18 constructed in accordance with the present invention. Although not illustrated, gun block 10 generally contains additional bullet assemblies in respective bores distributed along a vertical axis of the gun block.

Bullet assembly or bullet 18, near its rearward end, has spaced annular grooves which receive O-rings 19 19a to provide a fluid-tight seal for the bullet assembly 18 1n the bore 14, and flexible retrieving wires 20 are secured in a conventional manner between the .bullet assembly and gun block 10 to permit the bullet body of the assembly to be retrieved. A conventional igniter 21 suitably mounted in the block 10 may be employed to detonate the explosive propellant 17 and thereby propel the bullet 18 toward and into the formation.

Referring now to FIG. 2, the wire-retrieving connections 20 are omitted for clarity purposes. Bullet or bullet body member 18 includes a forward tubular core-receiving portion 21 and a rearward portion 22 received in bore 14 and sealed therein by O-rings 19, 19a. Forward portion 21 has a forwardly facing shoulder 24 which releasably receives a cutting ring or release member 25 and a snap ring 26 is provided to insure retention of ring 25 on the shoulder 24 of portion 21. Ring member 25 has the usual, conically shaped forward surface and is disposed slightly rearwardly of the forward cutting edge 27 on the tubular portion 21. Ring member 25 is also slightly greater in over-all diameter than the diameter of the body portion rearwardly of the cutting ring member to reduce the area of the bullet in the formation that is subject to hydrostatic pressure. The purpose of the cutting ring member 25 is to provide an oversized hole so that the outer body of the bullet 18 is prevented from intimate contact with the earth formations, the ring member 25 being left embedded in the earth formations. Of course, the precise connection and arrangement of the ring member relative to the bullet body is immaterial to the present invention so long as the ring member when in the earth formations is releasable from the bullet body.

The above-described ring arrangement, however, is preferable since the forward end of portion 21 extends beyond ring 25 and obtains a better core sample more reliably.

Tubular core portion 21 also has ports 28 in its side walls and connections 29 (shown in FIG. 1) for attachment of retrieving wire elements 20 to the bullet body.

Portion 22 of bullet 18 provides a bottom 30 for the tubular core portion 21 and has a chamber 31 opened by a rearward port 32 to the explosive 17. A ball 33 and spring 34 provide a one-way check valve for admitting pressure to chamber 31 via port 32 but preventing loss of pressure from the chamber. The bullet body 18 is also provided with a cylinder 35 receiving a piston 36 and associated rod member 37, the rod member being arranged to bear upon the cutting ring 25. The cylinder 35, behind the piston 36 in the body, opens to a restricted orifice and chamber portion 38 which, in turn, opens to chamber 31.

--In operation, when the powder 17 is ignited, the bullet is accelerated from bore 14 toward and into adjacent earth formations. Snap ring 26 is displaced from its groove leaving the cutting ring 25 free, the cutting ring staying on the bullet body due to the forward movement of the bullet body. As the forward end of the bullet penetrates the formation, the cutting ring makes a large hole and keeps the portion of the bullet rearwardly of the ring from intimate contact with the formation.

At the time of ignition of powder 17, explosively generated pressure is supplied to chamber 31 and this pressure, after being delayed by the restricted orifice and chamber portion 38, acts on piston 36 to displace the piston and associated rod member 37 to push the body member with a formation core out of the formation and through the release ring. This retracting operation takes place when the bullet is in the formation and the entire assembly with core, but less snap ring 26 and release ring 25, is subsequently returned with the retrieving wires 20 to the surface.

The apparatus of FIG. 3 is essentially the same as the apparatus of FIG. 2 except that between orifice and chamber portion 38, a collapsible chamber 40 is formed with a passageway 41, the chamber 40 having a piston 42. Chamber 40 is filled with a relatively non-compressible fluid such as water, oil, grease, jelly or a semi-solid such as soap or wax. This fluid in the chamber 40 will then be displaced through the orifice and chamber portion 38 under pressure to act on the piston 36 at a relatively slow rate .and provide a time delay insuring that the bullet enters the formation before the retracting function is performed. This insures the time delay required for self-retracting action.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A formation core-taking device adapted to be fired by an explosive charge from a gun body into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, means operatively coupled between said body member and said ring member and responsive to pressure for providing a force on said ring member, and time-delay means responsive to explosive pressures developed to fire said device from a gun body for applying pressure between said body member and said pressure-responsive means to urge said body member and said ring member in opposite directions when said ring member and forward end of said body member are embedded in earth formations so that said body member is moved relative to said ring member.

2. A formation core-taking device adapted to be fired from a gun body into earth formations about a well bore and comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably coupled on said forward end, rigid means for contacting said ring member, hydraulic time-delay means for moving said body member relative to said rigid means including collapsible chamber means normally containing a fluid and means in said body member for receiving said fluid at a controlled rate, and means responsive to explosive pressures developed to fire said core-taking device for actuating said hydraulic means after said core taking device leaves a gun body.

3. A formation core-taking device adapted to be fired from a gun body into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, means for producing a reaction force between said cutting ring member and said body member including a piston and cylinder, means for accumulating pressure from ignition of an explosive, and means for delaying application of such accumulated pressure to said piston and cylinder.

4. A formation core-taking device adapted to be fired from a gun body into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, means for producing .a reaction force between said cutting ring member and said body member including a piston and cylinder, a chamber with one-way valve means opening to an explosive for accumulating pressure from ignition of an explosive, and means for delaying application of such accumulated pressure to said piston and cylinder.

References Cited by the Examiner UNITED STATES PATENTS 2,809,805 10/1957 Laval -4 2,923,530 2/1960 Fields 1754 XR 3,072,202 1/1963 Brieger 175-4 3,101,797 8/1963 Brieger 1754 CHA LES E, OCQNNELL, Primary Examiner, 

3. A FORMATION CORE-TAKING DEVICE ADAPTED TO BE FIRED FROM A GUN BODY INTO EARTH FORMATIONS ABOUT A WELL BORE COMPRISING: A TUBULAR CORE-TAKING BODY MEMBER HAVING A FORWARD END, A FORMATION-CUTTING RING MEMBER RELEASABLY RECEIVED ON SAID FORWARD END, MEANS FOR PRODUCING A REACTION FORCE BETWEEN SAID CUTTING RING MEMBER AND SAID BODY MEMBER INCLUDING A PISTION AND CYLINDER, MEANS FOR ACCUMULATING PRESSURE FROM IGNITION OF AN EXPLOSIVE, AND MEANS FOR DELAYING APPLICATION OF SUCH ACCUMULATED PRESSURE TO SAID PISTON AND CYLINDER. 